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Dad's opinion matters — at least when it comes to predicting sibling relationships.

When adult children perceive that their fathers favor any particular child, there is a higher tendency of sibling tension in those families, according to a recent study conducted by Purdue University researchers that analyzed the relationships between 341 children in 174 families.

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The study, which appeared in the July issue of the Journal of Gerontology, Series B: Psychological Sciences and Social Sciences, found that favoritism by mothers did not as frequently lead to sibling tension.

"It indicates that these older dads have a special role in their children's lives," said Megan Gilligan, a Purdue doctoral student who is lead author on the article, "Differential Effects of Perceptions of Mothers' and Fathers' Favoritism on Sibling Tension in Adulthood."

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Jill Suitor, a professor of sociology and article co-author, said one reason for the findings could be due to the lower life expectancy in American fathers. Men have an average life expectancy of 76 years in the U.S., whereas women have an 81-year life expectancy, according to data from the Institute for Health Metrics and Evaluation.

"The importance of fathers' favoritism may come from these older adults noticing many of their friends' fathers no longer living, so they may value their dads even more than before; they realize their time together is limited," Suitor told the Journal & Courier (http://on.jconline.com/11JFdlY ).

Sisters Patricia Gaylord and Janet Burnett, both Lafayette residents, are taking care of aging parents. The two take turns visiting their parents, William and Ruth Nangle, almost every day. They said there isn't much favoritism or sibling rivalry in the family, so the findings of the study don't necessarily line up with their own experiences.

"We've always been friends," Burnett said.

When the sisters, along with two other siblings who live in Florida, were faced last year with the reality that their parents needed more hands-on care, it was Gaylord who stepped up for the day-to-day brunt of the job: William and Ruth would move in with her.

"There was no question," Gaylord said. "I wanted them to live with me."

But Gaylord's siblings stepped in when it seemed like the arrangement was getting too stressful: William had a few falls and Ruth's dementia worsened. Earlier this year, the Nangles moved into Creasy Springs Health Campus, a residential assisted-living community in Lafayette.

"We've always felt close and still do," said Gaylord.

"Except Dad says now that we're bossy," Burnett interjected, looking at her father with a smile.

"They've got a reason to be," William Nangle said.

The Purdue research is part of an ongoing look at parental favoritism funded by the National Institute on Aging. Suitor, Gilligan and Karl Pillemer, a professor of human development in the College of Human Ecology at Cornell University, have been working on the studies.

Previous research showed that favoritism by mothers caused sibling tension but did not take into account fathers.

In this study, researchers measured sibling tension in the number of arguments, disagreements or other issues that came up, along with other questions about real or perceived favoritism.

The researchers also asked the following question: "To which child in your family do you think your mother/father feels the most emotional closeness?"

In the study, sibling tension as a result of favoritism was more pronounced in daughters. Because fathers typically invest more in their sons, a father's favoritism shown toward daughters may violate that norm and result in greater sibling tension, Gilligan said.

"For these reasons, when adult children perceive their fathers as engaging in favoritism, there may be greater concern about competition for his affection and support, resulting in higher levels of sibling tension," she said.

In West Lafayette, the Johnsons are familiar with trying to avoid creating perceptions of favoritism in their family of six.

Triplets Kristen, Lauren and Evan Johnson are all athletes and musicians at West Lafayette High School. An older daughter, Crystal, no longer lives at home.

Their father, Keith Johnson, said he takes steps to give all his children equal attention, despite who scores a goal or aces a test on a given day.

"Frankly, I try to avoid comparisons," Johnson said. "It may inadvertently happen, but I think I'm cognizant of that, to try not to do that."

Lauren Johnson said the siblings also do their part to avoid creating tension or competition among siblings.

"We never try to be like, 'Did you see me pass Kristen?' " she said.

Keith Johnson, who has two aging parents, said he hopes that helps their relationship later in life when it comes time to take care of him.

"When you're older, you focus less on yourself and more on the dynamic of the moment," he said. "It could be the well-being of one of them, or somebody else."

The researchers hope that in the study's next wave they can dial into the emotions and parenting styles of the surveyed adult's children to see if perceptions of favoritism are passed down generation to generation.